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Linux/fs/btrfs/xattr.c

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  1 /*
  2  * Copyright (C) 2007 Red Hat.  All rights reserved.
  3  *
  4  * This program is free software; you can redistribute it and/or
  5  * modify it under the terms of the GNU General Public
  6  * License v2 as published by the Free Software Foundation.
  7  *
  8  * This program is distributed in the hope that it will be useful,
  9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 11  * General Public License for more details.
 12  *
 13  * You should have received a copy of the GNU General Public
 14  * License along with this program; if not, write to the
 15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 16  * Boston, MA 021110-1307, USA.
 17  */
 18 
 19 #include <linux/init.h>
 20 #include <linux/fs.h>
 21 #include <linux/slab.h>
 22 #include <linux/rwsem.h>
 23 #include <linux/xattr.h>
 24 #include <linux/security.h>
 25 #include <linux/posix_acl_xattr.h>
 26 #include "ctree.h"
 27 #include "btrfs_inode.h"
 28 #include "transaction.h"
 29 #include "xattr.h"
 30 #include "disk-io.h"
 31 #include "props.h"
 32 #include "locking.h"
 33 
 34 
 35 ssize_t __btrfs_getxattr(struct inode *inode, const char *name,
 36                                 void *buffer, size_t size)
 37 {
 38         struct btrfs_dir_item *di;
 39         struct btrfs_root *root = BTRFS_I(inode)->root;
 40         struct btrfs_path *path;
 41         struct extent_buffer *leaf;
 42         int ret = 0;
 43         unsigned long data_ptr;
 44 
 45         path = btrfs_alloc_path();
 46         if (!path)
 47                 return -ENOMEM;
 48 
 49         /* lookup the xattr by name */
 50         di = btrfs_lookup_xattr(NULL, root, path, btrfs_ino(BTRFS_I(inode)),
 51                         name, strlen(name), 0);
 52         if (!di) {
 53                 ret = -ENODATA;
 54                 goto out;
 55         } else if (IS_ERR(di)) {
 56                 ret = PTR_ERR(di);
 57                 goto out;
 58         }
 59 
 60         leaf = path->nodes[0];
 61         /* if size is 0, that means we want the size of the attr */
 62         if (!size) {
 63                 ret = btrfs_dir_data_len(leaf, di);
 64                 goto out;
 65         }
 66 
 67         /* now get the data out of our dir_item */
 68         if (btrfs_dir_data_len(leaf, di) > size) {
 69                 ret = -ERANGE;
 70                 goto out;
 71         }
 72 
 73         /*
 74          * The way things are packed into the leaf is like this
 75          * |struct btrfs_dir_item|name|data|
 76          * where name is the xattr name, so security.foo, and data is the
 77          * content of the xattr.  data_ptr points to the location in memory
 78          * where the data starts in the in memory leaf
 79          */
 80         data_ptr = (unsigned long)((char *)(di + 1) +
 81                                    btrfs_dir_name_len(leaf, di));
 82         read_extent_buffer(leaf, buffer, data_ptr,
 83                            btrfs_dir_data_len(leaf, di));
 84         ret = btrfs_dir_data_len(leaf, di);
 85 
 86 out:
 87         btrfs_free_path(path);
 88         return ret;
 89 }
 90 
 91 static int do_setxattr(struct btrfs_trans_handle *trans,
 92                        struct inode *inode, const char *name,
 93                        const void *value, size_t size, int flags)
 94 {
 95         struct btrfs_dir_item *di = NULL;
 96         struct btrfs_root *root = BTRFS_I(inode)->root;
 97         struct btrfs_fs_info *fs_info = root->fs_info;
 98         struct btrfs_path *path;
 99         size_t name_len = strlen(name);
100         int ret = 0;
101 
102         if (name_len + size > BTRFS_MAX_XATTR_SIZE(root->fs_info))
103                 return -ENOSPC;
104 
105         path = btrfs_alloc_path();
106         if (!path)
107                 return -ENOMEM;
108         path->skip_release_on_error = 1;
109 
110         if (!value) {
111                 di = btrfs_lookup_xattr(trans, root, path,
112                                 btrfs_ino(BTRFS_I(inode)), name, name_len, -1);
113                 if (!di && (flags & XATTR_REPLACE))
114                         ret = -ENODATA;
115                 else if (IS_ERR(di))
116                         ret = PTR_ERR(di);
117                 else if (di)
118                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
119                 goto out;
120         }
121 
122         /*
123          * For a replace we can't just do the insert blindly.
124          * Do a lookup first (read-only btrfs_search_slot), and return if xattr
125          * doesn't exist. If it exists, fall down below to the insert/replace
126          * path - we can't race with a concurrent xattr delete, because the VFS
127          * locks the inode's i_mutex before calling setxattr or removexattr.
128          */
129         if (flags & XATTR_REPLACE) {
130                 ASSERT(inode_is_locked(inode));
131                 di = btrfs_lookup_xattr(NULL, root, path,
132                                 btrfs_ino(BTRFS_I(inode)), name, name_len, 0);
133                 if (!di)
134                         ret = -ENODATA;
135                 else if (IS_ERR(di))
136                         ret = PTR_ERR(di);
137                 if (ret)
138                         goto out;
139                 btrfs_release_path(path);
140                 di = NULL;
141         }
142 
143         ret = btrfs_insert_xattr_item(trans, root, path, btrfs_ino(BTRFS_I(inode)),
144                                       name, name_len, value, size);
145         if (ret == -EOVERFLOW) {
146                 /*
147                  * We have an existing item in a leaf, split_leaf couldn't
148                  * expand it. That item might have or not a dir_item that
149                  * matches our target xattr, so lets check.
150                  */
151                 ret = 0;
152                 btrfs_assert_tree_locked(path->nodes[0]);
153                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
154                 if (!di && !(flags & XATTR_REPLACE)) {
155                         ret = -ENOSPC;
156                         goto out;
157                 }
158         } else if (ret == -EEXIST) {
159                 ret = 0;
160                 di = btrfs_match_dir_item_name(fs_info, path, name, name_len);
161                 ASSERT(di); /* logic error */
162         } else if (ret) {
163                 goto out;
164         }
165 
166         if (di && (flags & XATTR_CREATE)) {
167                 ret = -EEXIST;
168                 goto out;
169         }
170 
171         if (di) {
172                 /*
173                  * We're doing a replace, and it must be atomic, that is, at
174                  * any point in time we have either the old or the new xattr
175                  * value in the tree. We don't want readers (getxattr and
176                  * listxattrs) to miss a value, this is specially important
177                  * for ACLs.
178                  */
179                 const int slot = path->slots[0];
180                 struct extent_buffer *leaf = path->nodes[0];
181                 const u16 old_data_len = btrfs_dir_data_len(leaf, di);
182                 const u32 item_size = btrfs_item_size_nr(leaf, slot);
183                 const u32 data_size = sizeof(*di) + name_len + size;
184                 struct btrfs_item *item;
185                 unsigned long data_ptr;
186                 char *ptr;
187 
188                 if (size > old_data_len) {
189                         if (btrfs_leaf_free_space(fs_info, leaf) <
190                             (size - old_data_len)) {
191                                 ret = -ENOSPC;
192                                 goto out;
193                         }
194                 }
195 
196                 if (old_data_len + name_len + sizeof(*di) == item_size) {
197                         /* No other xattrs packed in the same leaf item. */
198                         if (size > old_data_len)
199                                 btrfs_extend_item(fs_info, path,
200                                                   size - old_data_len);
201                         else if (size < old_data_len)
202                                 btrfs_truncate_item(fs_info, path,
203                                                     data_size, 1);
204                 } else {
205                         /* There are other xattrs packed in the same item. */
206                         ret = btrfs_delete_one_dir_name(trans, root, path, di);
207                         if (ret)
208                                 goto out;
209                         btrfs_extend_item(fs_info, path, data_size);
210                 }
211 
212                 item = btrfs_item_nr(slot);
213                 ptr = btrfs_item_ptr(leaf, slot, char);
214                 ptr += btrfs_item_size(leaf, item) - data_size;
215                 di = (struct btrfs_dir_item *)ptr;
216                 btrfs_set_dir_data_len(leaf, di, size);
217                 data_ptr = ((unsigned long)(di + 1)) + name_len;
218                 write_extent_buffer(leaf, value, data_ptr, size);
219                 btrfs_mark_buffer_dirty(leaf);
220         } else {
221                 /*
222                  * Insert, and we had space for the xattr, so path->slots[0] is
223                  * where our xattr dir_item is and btrfs_insert_xattr_item()
224                  * filled it.
225                  */
226         }
227 out:
228         btrfs_free_path(path);
229         return ret;
230 }
231 
232 /*
233  * @value: "" makes the attribute to empty, NULL removes it
234  */
235 int __btrfs_setxattr(struct btrfs_trans_handle *trans,
236                      struct inode *inode, const char *name,
237                      const void *value, size_t size, int flags)
238 {
239         struct btrfs_root *root = BTRFS_I(inode)->root;
240         int ret;
241 
242         if (btrfs_root_readonly(root))
243                 return -EROFS;
244 
245         if (trans)
246                 return do_setxattr(trans, inode, name, value, size, flags);
247 
248         trans = btrfs_start_transaction(root, 2);
249         if (IS_ERR(trans))
250                 return PTR_ERR(trans);
251 
252         ret = do_setxattr(trans, inode, name, value, size, flags);
253         if (ret)
254                 goto out;
255 
256         inode_inc_iversion(inode);
257         inode->i_ctime = current_time(inode);
258         set_bit(BTRFS_INODE_COPY_EVERYTHING, &BTRFS_I(inode)->runtime_flags);
259         ret = btrfs_update_inode(trans, root, inode);
260         BUG_ON(ret);
261 out:
262         btrfs_end_transaction(trans);
263         return ret;
264 }
265 
266 ssize_t btrfs_listxattr(struct dentry *dentry, char *buffer, size_t size)
267 {
268         struct btrfs_key key;
269         struct inode *inode = d_inode(dentry);
270         struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
271         struct btrfs_root *root = BTRFS_I(inode)->root;
272         struct btrfs_path *path;
273         int ret = 0;
274         size_t total_size = 0, size_left = size;
275 
276         /*
277          * ok we want all objects associated with this id.
278          * NOTE: we set key.offset = 0; because we want to start with the
279          * first xattr that we find and walk forward
280          */
281         key.objectid = btrfs_ino(BTRFS_I(inode));
282         key.type = BTRFS_XATTR_ITEM_KEY;
283         key.offset = 0;
284 
285         path = btrfs_alloc_path();
286         if (!path)
287                 return -ENOMEM;
288         path->reada = READA_FORWARD;
289 
290         /* search for our xattrs */
291         ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
292         if (ret < 0)
293                 goto err;
294 
295         while (1) {
296                 struct extent_buffer *leaf;
297                 int slot;
298                 struct btrfs_dir_item *di;
299                 struct btrfs_key found_key;
300                 u32 item_size;
301                 u32 cur;
302 
303                 leaf = path->nodes[0];
304                 slot = path->slots[0];
305 
306                 /* this is where we start walking through the path */
307                 if (slot >= btrfs_header_nritems(leaf)) {
308                         /*
309                          * if we've reached the last slot in this leaf we need
310                          * to go to the next leaf and reset everything
311                          */
312                         ret = btrfs_next_leaf(root, path);
313                         if (ret < 0)
314                                 goto err;
315                         else if (ret > 0)
316                                 break;
317                         continue;
318                 }
319 
320                 btrfs_item_key_to_cpu(leaf, &found_key, slot);
321 
322                 /* check to make sure this item is what we want */
323                 if (found_key.objectid != key.objectid)
324                         break;
325                 if (found_key.type > BTRFS_XATTR_ITEM_KEY)
326                         break;
327                 if (found_key.type < BTRFS_XATTR_ITEM_KEY)
328                         goto next_item;
329 
330                 di = btrfs_item_ptr(leaf, slot, struct btrfs_dir_item);
331                 item_size = btrfs_item_size_nr(leaf, slot);
332                 cur = 0;
333                 while (cur < item_size) {
334                         u16 name_len = btrfs_dir_name_len(leaf, di);
335                         u16 data_len = btrfs_dir_data_len(leaf, di);
336                         u32 this_len = sizeof(*di) + name_len + data_len;
337                         unsigned long name_ptr = (unsigned long)(di + 1);
338 
339                         if (verify_dir_item(fs_info, leaf, di)) {
340                                 ret = -EIO;
341                                 goto err;
342                         }
343 
344                         total_size += name_len + 1;
345                         /*
346                          * We are just looking for how big our buffer needs to
347                          * be.
348                          */
349                         if (!size)
350                                 goto next;
351 
352                         if (!buffer || (name_len + 1) > size_left) {
353                                 ret = -ERANGE;
354                                 goto err;
355                         }
356 
357                         read_extent_buffer(leaf, buffer, name_ptr, name_len);
358                         buffer[name_len] = '\0';
359 
360                         size_left -= name_len + 1;
361                         buffer += name_len + 1;
362 next:
363                         cur += this_len;
364                         di = (struct btrfs_dir_item *)((char *)di + this_len);
365                 }
366 next_item:
367                 path->slots[0]++;
368         }
369         ret = total_size;
370 
371 err:
372         btrfs_free_path(path);
373 
374         return ret;
375 }
376 
377 static int btrfs_xattr_handler_get(const struct xattr_handler *handler,
378                                    struct dentry *unused, struct inode *inode,
379                                    const char *name, void *buffer, size_t size)
380 {
381         name = xattr_full_name(handler, name);
382         return __btrfs_getxattr(inode, name, buffer, size);
383 }
384 
385 static int btrfs_xattr_handler_set(const struct xattr_handler *handler,
386                                    struct dentry *unused, struct inode *inode,
387                                    const char *name, const void *buffer,
388                                    size_t size, int flags)
389 {
390         name = xattr_full_name(handler, name);
391         return __btrfs_setxattr(NULL, inode, name, buffer, size, flags);
392 }
393 
394 static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
395                                         struct dentry *unused, struct inode *inode,
396                                         const char *name, const void *value,
397                                         size_t size, int flags)
398 {
399         name = xattr_full_name(handler, name);
400         return btrfs_set_prop(inode, name, value, size, flags);
401 }
402 
403 static const struct xattr_handler btrfs_security_xattr_handler = {
404         .prefix = XATTR_SECURITY_PREFIX,
405         .get = btrfs_xattr_handler_get,
406         .set = btrfs_xattr_handler_set,
407 };
408 
409 static const struct xattr_handler btrfs_trusted_xattr_handler = {
410         .prefix = XATTR_TRUSTED_PREFIX,
411         .get = btrfs_xattr_handler_get,
412         .set = btrfs_xattr_handler_set,
413 };
414 
415 static const struct xattr_handler btrfs_user_xattr_handler = {
416         .prefix = XATTR_USER_PREFIX,
417         .get = btrfs_xattr_handler_get,
418         .set = btrfs_xattr_handler_set,
419 };
420 
421 static const struct xattr_handler btrfs_btrfs_xattr_handler = {
422         .prefix = XATTR_BTRFS_PREFIX,
423         .get = btrfs_xattr_handler_get,
424         .set = btrfs_xattr_handler_set_prop,
425 };
426 
427 const struct xattr_handler *btrfs_xattr_handlers[] = {
428         &btrfs_security_xattr_handler,
429 #ifdef CONFIG_BTRFS_FS_POSIX_ACL
430         &posix_acl_access_xattr_handler,
431         &posix_acl_default_xattr_handler,
432 #endif
433         &btrfs_trusted_xattr_handler,
434         &btrfs_user_xattr_handler,
435         &btrfs_btrfs_xattr_handler,
436         NULL,
437 };
438 
439 static int btrfs_initxattrs(struct inode *inode,
440                             const struct xattr *xattr_array, void *fs_info)
441 {
442         const struct xattr *xattr;
443         struct btrfs_trans_handle *trans = fs_info;
444         char *name;
445         int err = 0;
446 
447         for (xattr = xattr_array; xattr->name != NULL; xattr++) {
448                 name = kmalloc(XATTR_SECURITY_PREFIX_LEN +
449                                strlen(xattr->name) + 1, GFP_KERNEL);
450                 if (!name) {
451                         err = -ENOMEM;
452                         break;
453                 }
454                 strcpy(name, XATTR_SECURITY_PREFIX);
455                 strcpy(name + XATTR_SECURITY_PREFIX_LEN, xattr->name);
456                 err = __btrfs_setxattr(trans, inode, name,
457                                        xattr->value, xattr->value_len, 0);
458                 kfree(name);
459                 if (err < 0)
460                         break;
461         }
462         return err;
463 }
464 
465 int btrfs_xattr_security_init(struct btrfs_trans_handle *trans,
466                               struct inode *inode, struct inode *dir,
467                               const struct qstr *qstr)
468 {
469         return security_inode_init_security(inode, dir, qstr,
470                                             &btrfs_initxattrs, trans);
471 }
472 

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